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Re: EAGAIN in "read jobs pipe"

From: james coleman
Subject: Re: EAGAIN in "read jobs pipe"
Date: Wed, 10 Jan 2007 11:09:06 +0000
User-agent: Thunderbird (X11/20060909)

Oh dear. Sorry people. I was of course being a bit silly when talking about 
make -j 16385!

Howard Chu wrote:
address@hidden wrote:
 Perhaps... On the other hand, if you're using -j 65K, why not
just -j? Does you build even have 65K jobs?

of course I do not use -j65k ! :-O :-)

Very good question.
I could be wrong of course, but I in my experience you don't gain any
real benefit from going beyond 3-4 jobs per (virtual) core... What's the
difference in build time from, say, -j 128 and -j 65385 for you?

.... not much!

also a build making more calls to make can result in
 jfactor * number of make calls jobs

So I might regularily use maybe -j 10 (when I know 10 more calls to make are 
On some machines this might be unacceptable and bring them to their knees.
On other machines it can work really well.

I usually count on 1.5 jobs per core, but obviously the right balance depends on your disk speeds relative to your CPUs...

I find that the limiting factor in the speed of builds is disk access.
 (gcc preprocessing following all header files)
So all of the multiple processes spawned are mostly just waiting on disk.
So using a parallel build makes optimum use of both cpu & disk together.

So yes, between 3-4 jobs per core, maybe a little bit more.

Of course Your Mile^H^H^H^HKilometerage Will Vary alot with different projects 
and machines.


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